The efficiency of an air diffusion system consists of two factors. The first is the ability of the system to remove heat and contaminants out of the ventilated room. This is most often characterized using temperature removal and contaminant removal efficiency. The second, seldom considered, factor is the uniformity of the temperature and contaminant distribution within the ventilated space. This factor describes how much the maximum contaminant concentration or minimum temperature differs from the average value.
The contaminant removal efficiency and the uniformity of contaminant concentration in the occupied zone of a room were studied in scale model with the following varying parameters : occupied zone obstruction level, air distribution system, air change rate, cooling load, contaminant sources distribution.
Results show that obstruction level, air distribution system, air change rate and cooling load have a small influence on contaminant removal efficiency and uniformity of contaminant concentration.
There is a variety of different methods consulting engineers use to design room system, room air diffusion, such as assumption of perfect mixing, design methods employing the empirical relations determined through research, air jet theory and computational fluid dynamics (CFD) codes. The most common design methods based on air jet theory allows only for the prediction of extreme values of air velocities and air temperatures in the occupied zone.
Recently indoor air quality (IAQ) became an important issue and as a result researchers have developed a large number of different air quality indicators. This study focuses on air exchange efficiency (ea) and contaminant removal effectiveness (e) as suitable indicators for use in design and on-site measurements. These two IAQ indicators were numerically studied and compared for five typical indoor spaces with different ventilation strategies and contaminant sources. Overall,
Germicidal UV (UVC) lamps have a long history of use for inactivation of microbial aerosols. The majority of the literature has considered control of infectious diseases, such as tuberculosis (TB) in medical facilities. Emphasis has recently been on ventilation duct use of UVC. Under these conditions, infections agents are usually of less concern than environmental organisms. Much less information is available regarding common environmental organisms. The present work reports the ability of UVC lamps to inactivate 7 representative microbial aerosols in ventilation duct conditions.
Published guidelines on mold remediation do not specify sampling protocols to measure the efficacy of remediation efforts. The purpose of this study was to evaluate fungal remediation of contaminated ducts by comparing the amount of residual surface contamination to the amount in new ducts. Fungal contamination of galvanized metal and rigid fibrous glass ducts were evaluated using fluorometric and microscopic methods. Fungal contamination was measured in newly installed ducts in addition to pre- and post-remediation. Newly installed ducts had low levels of fungal debris.
The contaminant emission rate is an important parameter describing the potential for materials to affect indoor air quality through the release of volatile organic compounds (VOCs). Emission rates have traditionally been inferred from gas-phase concentration measurements obtained through chamber studies. However, models suggest that the rate at which VOCs are emitted by diffusion-controlled materials may be influenced by ventilation rates.
On 75 air outlets of HVAC systems from 12 participating companies, fungal contamination was measured and compared to the incoming fresh air. For one of them with a significantly high level of fungi, dominated by one penicillium species, regular checks on a period of 14 months have been realised. The study concludes that this kind of measurement can be used as an indicator of the HVAC system hygienic condition.
The effectiveness of a ventilation system in terms of the age of air and its ability to remove contaminants will be significantly affected if part of the exhaust air is recirculated. In this paper the consequences of recirculation of air in mechanical ventilation systems on ventilation effectiveness parameters is examined. Two alternative methods of establishing ventilation effectiveness parameters relating to air change efficiency and contaminant removal effectiveness when recirculation of air is present are presented.